1. Field of the Invention
The present invention relates to a scroll thrust bearing, and more particularly to a thrust bearing having plural double tapered rollers as rolling elements preferably used for axial load support structure in, for example, scroll type compressor.
2. Description of the Related Art
A scroll type compressor is a kind of rotary compressor, in which compression of fluid is continuous, and torque fluctuations and vibrations are smaller as compared with the conventional reciprocating compressor and high speed operation is possible, and hence it is intensively developed recently.
This kind of compressor comprises a axial load support structure for enabling its scroll drive. This support structure is a so-called built-in type, being integrally assembled in the compressor, and a kind of thrust bearing is composed, and a bearing called a ball coupling for use in such position has been already known as an independent mechanical element.
Anyway, steel balls or similar spheres are used as rolling elements, but such spheres support in point contact state, and are hence small in load capacity and inferior in durability, not withstanding long-term use in high speed and high load condition, and there were problems in the service life. In addition, assembling was difficult because each sphere must be incorporated when assembling the compressor.
To solve such problems, a scroll type compressor comprising a axial load support structure is proposed as shown in FIG. 10(a) (for example, Japanese Laid-open Utility Model No. 61-82086, Japanese Laid-open Patent No. 62-107284).
In the scroll constitution of this compressor, as shown in the diagram, a fixed scroll member (c) having a volute (b) is fixed in a housing (a), and a swivel scroll member (e) having a volute (d) to be engaged with the volume (b) is supported on a axial load support structure (f) so as to be free to swivel or revolve, while this swivel scroll member (e) is driven as being coupled to a drive source not shown in the drawing through a crankpin (g).
The support structure (f) is formed as a kind of thrust bearing, and plural pockets (h), (i) are disposed oppositely at the inner side of the housing (a) and the facing side of the swivel scroll member (e), while double conical rolling elements R (double tapered rollers) are interposed between the both pockets (h) and (i) so as to roll between them.
By the rotary drive of the crankpin (g), the swivel scroll member (e) swivels or rotates without revolving on the fixed scroll member (c), and the fluid gas sucked in from a suction port (j) is compressed in a compression chamber formed between the volutes (b) and (d), and is discharged through a discharge port (k).
In this case, as shown schematically in FIG. 10(b), the double tapered rollers R captured in the pockets (h), (i) make rolling motions while their conical surfaces Ra, Rb are in a linear contact state with flat bottoms (m), (n) of the pockets (h), (i). These double tapered rollers R, R, . . . arrest relative rotation of both scroll members (c), (e) (revolution of the swivel scroll member (e)) when the swivel scroll member (e) swivels on the fixed scroll member (c) (this swivel route coincides with the route indicated by arrow (o) in FIG. 10(b)).
A roller bearing preferably used as such axial load support structure (f) has been also proposed (for example, Japanese Laid-open Patent No. 62-274113, and Japanese Laid-open Patent No. 7-119741).
This roller bearing is shown in FIG. 11(a) and FIG. 11(b), in which a plurality of double tapered rollers R, R, . . . are interposed between a pair of parallel bearing plates (p) and (q) so as to roll between them. The double tapered rollers R are held in a pair of pockets (h), (i) provided oppositely in the bearing plates (p), (q). These pockets (h), (i) are circular in shape having an inside diameter corresponding to the relative swivel route (o) of the both bearing plats (p), (q), and either like the pocket (h) of the bearing plate (p), a track plate (r) having a track forming surface and a holding plate (s) having a pocket forming hole are integrally laminated and fixed, or like the pocket (i) of the bearing plate (q), it is directly formed on a single bearing plate (q).
In the pockets (h), (i), the double tapered rollers R make rolling motions as shown in FIG. 10(b), so as to guarantee relative and smooth swivel of the both bearing plates (p), (q), while arresting relative rotation of the both bearing plates (p), (q).
According to such double tapered rollers R, R, . . . or the axial load support structure (f) using roller bearings, as compared with the conventional constitution using rolling elements composed of spheres, the durability is improved outstandingly, and it sufficiently withstands long-term use in high speed and high load condition.
In spite of such excellent durability, however, in the scroll type compressor having such axial load support structure (f) is not realized yet at the present because the assembling and manufacturing technology of the axial mass-produce at low cost and high precision, and it is far from the practical level.